Zero-Cross

The term zero-cross or synchronous operation of SCR's is derived from the fact that the SCR's are turned on only when the instantaneous value of the sinusoidal waveform is zero.

In zero-cross operation power is applied for a number of continuous half-cycles and then removed for a number of half-cycles to achieve the desired load power in the same manner as power would be controlled with a mechanical switching device. 

Zero-Cross SCR Power Controllers

Model Phases Firing Mode Output Current Low Current High Highlights
MicroFUSION Single Phase Single phase Phase angle, Zero cross, Zero Cross Transformer Mode, Fast Zero Cross AC 8 400

MicroFUSION is an ultra-compact high performance digital SCR controller that adapts to the analog environment as well as the digital environment. 
MicroFUSION Three Phase Three phase Phase angle, Zero cross, Zero Cross Transformer Mode, Fast Zero Cross AC 8 400

MicroFUSION is an ultra-compact high performance digital SCR controller that adapts to the analog environment as well as the digital environment.
FUSION Single Phase (AC) Power Controller 500 - 1200A Single phase Phase angle, Zero cross, Fast Zero Cross AC 500 1 200

24 - 600 Vac. A microprocessor-based SCR controller operating both analog and digital interfaces. A phase angle or zero cross fired controller which linearly controls, with respect to the setpoint, the AC voltage, current, or true power applied to an electrical load. Control is achieved by means of a pair of inverse parallel SCRs.
FUSION Three Phase (AC) Power Controller 500 - 1200A Three phase Phase angle, Zero cross, Fast Zero Cross AC 500 1 200

24 - 600 Vac. A microprocessor-based SCR controller operating both analog and digital interfaces. A phase angle or zero cross fired SCR controller which linearly controls, with respect to the setpoint, the AC voltage, current, or true power applied to a three phase electrical load. The 3 phase controller can be ordered in either 2 or 3 leg control with 2 leg being limited to zero cross firing. Control is achieved for 3 leg by three pairs of inverse parallel SCRs or in 2 leg by 2 pairs of inverse parallel SCRs.